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Commit b92a953c authored by Mark Rutland's avatar Mark Rutland Committed by Linus Torvalds
Browse files

lib/test_kasan.c: add roundtrip tests 

In several places we need to be able to operate on pointers which have
gone via a roundtrip:

	virt -> {phys,page} -> virt

With KASAN_SW_TAGS, we can't preserve the tag for SLUB objects, and the
{phys,page} -> virt conversion will use KASAN_TAG_KERNEL.

This patch adds tests to ensure that this works as expected, without
false positives which have recently been spotted [1,2] in testing.

[1] https://lore.kernel.org/linux-arm-kernel/20190819114420.2535-1-walter-zh.wu@mediatek.com/
[2] https://lore.kernel.org/linux-arm-kernel/20190819132347.GB9927@lakrids.cambridge.arm.com/

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190821153927.28630-1-mark.rutland@arm.com


Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Tested-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Acked-by: default avatarAndrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ae8f06b3

lib/test_kasan.c

+41 −0
Original line number Diff line number Diff line
@@ -18,6 +18,9 @@ 
#include <linux/slab.h>

#include <linux/string.h>

#include <linux/uaccess.h>

#include <linux/io.h>



#include <asm/page.h>



/*

 * Note: test functions are marked noinline so that their names appear in
@@ -337,6 +340,42 @@ static noinline void __init kmalloc_uaf2(void) 
	kfree(ptr2);

}



static noinline void __init kfree_via_page(void)

{

	char *ptr;

	size_t size = 8;

	struct page *page;

	unsigned long offset;



	pr_info("invalid-free false positive (via page)\n");

	ptr = kmalloc(size, GFP_KERNEL);

	if (!ptr) {

		pr_err("Allocation failed\n");

		return;

	}



	page = virt_to_page(ptr);

	offset = offset_in_page(ptr);

	kfree(page_address(page) + offset);

}



static noinline void __init kfree_via_phys(void)

{

	char *ptr;

	size_t size = 8;

	phys_addr_t phys;



	pr_info("invalid-free false positive (via phys)\n");

	ptr = kmalloc(size, GFP_KERNEL);

	if (!ptr) {

		pr_err("Allocation failed\n");

		return;

	}



	phys = virt_to_phys(ptr);

	kfree(phys_to_virt(phys));

}



static noinline void __init kmem_cache_oob(void)

{

	char *p;
@@ -737,6 +776,8 @@ static int __init kmalloc_tests_init(void) 
	kmalloc_uaf();

	kmalloc_uaf_memset();

	kmalloc_uaf2();

	kfree_via_page();

	kfree_via_phys();

	kmem_cache_oob();

	memcg_accounted_kmem_cache();

	kasan_stack_oob();